Disk drives are information storage devices that use magnetic media to store data and a movable read/write head positioned over the magnetic media to selectively read data from and write data to the magnetic media.
Consumers are constantly desiring greater storage capacity for such disk drive devices, as well as faster and more accurate reading and writing operations. Thus, disk drive manufacturers have continued to develop higher capacity disk drives by, for example, increasing the density of the information tracks on the disks by using a narrower track width and/or a narrower track pitch. However, each increase in track density requires that the disk drive device have a corresponding increase in the positional control of the read/write head in order to enable quick and accurate reading and writing operations using the higher density disks. As track density increases, it becomes more and more difficult using known technology to quickly and accurately position the read/write head over the desired information tracks on the storage media. Thus, disk drive manufacturers are constantly seeking ways to improve the positional control of the read/write head in order to take advantage of the continual increases in track density.
One approach that has been effectively used by disk drive manufacturers to improve the positional control of read/write heads for higher density disks is to employ a secondary actuator, known as a micro-actuator, that works in conjunction with a primary actuator to enable quick and accurate positional control for the read/write head. Disk drives that incorporate a micro-actuator are known as dual-stage actuator systems.
Various dual-stage actuator systems have been developed in the past for the purpose of increasing the access speed and fine tuning the position of the read/write head over the desired tracks on high density storage media. Such dual-stage actuator systems typically include a primary voice-coil motor (VCM) actuator and a secondary micro-actuator, such as a PZT element micro-actuator. The VCM actuator is controlled by a servo control system that rotates the actuator arm that supports the read/write head to position the read/write head over the desired information track on the storage media. The PZT element micro-actuator is used in conjunction with the VCM actuator for the purpose of increasing the positioning access speed and fine tuning the exact position of the read/write head over the desired track. Thus, the VCM actuator makes larger adjustments to the position of the read/write head, while the PZT element micro-actuator makes smaller adjustments that fine tune the position of the read/write head relative to the storage media. In conjunction, the VCM actuator and the PZT element micro-actuator enable information to be efficiently and accurately written to and read from high density storage media.
One known type of micro-actuator incorporates PZT elements for causing fine positional adjustments of the read/write head. Such PZT micro-actuators include associated electronics that are operable to excite the PZT elements on the micro-actuator to selectively cause expansion or contraction thereof. The PZT micro-actuator is configured such that expansion or contraction of the PZT elements causes movement of the micro-actuator which, in turn, causes movement of the read/write head. This movement is used to make faster and finer adjustments to the position of the read/write head, as compared to a disk drive unit that uses only a VCM actuator. Such PZT elements have been disclosed in various open literatures, for example, U.S. Patent NO. 2003-0168935, entitled “Piezoelectric Driving Device”.
FIG. 1a shows a magnetic disk 101 mounted on a spindle motor 102 for spinning the disk 101. A voice coil motor arm 104 carries a HGA 100 that includes a micro-actuator 105 with a slider 103 incorporating a read/write head. A voice-coil motor (VCM) is provided for controlling the motion of the motor arm 104 and, in turn, controlling the slider 103 to move from track to track across the surface of the disk 101, thereby enabling the read/write head to read data from or write data to the disk 101. In operation, a lift force is generated by the aerodynamic interaction between the slider 103 and the spinning magnetic disk 101. The lift force is opposed by equal and opposite spring forces applied by a suspension of the HGA 100 such that a predetermined flying height above the surface of the spinning disk 101 is maintained over full radial stroke of the motor arm 104.
Because of the inherent tolerances that exist in the placement of the slider 103 by a VCM alone, the slider 103 cannot achieve quick and fine position control, which adversely impacts the ability of the read/write head to accurately read data from and write data to the disk. As a result, a PZT micro-actuator 105, as described above, is provided in order to improve the position control of the slider 103 and the read/write head. More particularly, the PZT micro-actuator 105 corrects the displacement of the slider 103 on a much smaller scale, as compared to the VCM, in order to compensate for the resonance tolerance of the VCM and/or head suspension assembly. The micro-actuator 105 enables, for example, the use of a smaller recording track pitch, and can increase the “tracks per inch” (TPI) value by 50% for the disk drive unit, as well as provide an advantageous reduction in the head seeking and settling time. Thus, the PZT micro-actuator 105 enables the disk drive unit to have a significant increase in the surface recording density of the information storage disks used therein.
Referring to FIGS. 1b-1c, the HGA 100 includes the slider 103, a pair of thin film PZT elements 10 for fine positional adjustments of the slider 103, and a suspension to support the slider 103 and the PZT elements 10. The suspension comprises a flexure 122, a slider support 121, a metal base 123, and a load beam 124.
As shown in FIGS. 1b-1c, the slider 103 is partially mounted on the slider support 121 of the suspension, and a bump 127 formed on the slider support 121 supports the center of the back surface of the slider 103. The flexure 122 with a plurality of traces couples the slider support 121 and the metal base 123. The load beam 124 is provided under the slider support 121 and the metal base 123 to support both of them. The load beam 124 forms a dimple 125 thereon that works with the bump 127. When the slider 103 is flying on the disk, the dimple 125 supports the bump 127, which keeps the load force from the load beam 124 always evenly applying to the center of the slider 103, thus ensure the slider 103 a good fly performance, such as good fly posture. The flexure 122 provides a tongue region 128 thereof for positioning the PZT elements 10. The two PZT elements 10 are attached on the tongue region 128 of the flexure 122. With reference to FIG. 1c, when a voltage is input to the thin film PZT elements 10, one of the PZT elements 10 may contract as shown by arrow D, and the other one may expand as shown by arrow E. This will generate a rotation torque that causes the slider support 121 to rotate in the arrowed direction C and, in turn, makes the slider 103 move.
Since the slider 103 is partially mounted on the slider support 121 and the bump 127 of the slider support 121 supports the center of the slider 103, the slider 103 with the slider support 121 are easy to rotate against the dimple 125. The slider support 121 is coupled with the metal base 123 by the tongue region 128 of the flexure 122. Since the thickness of the tongue region 128 of the flexure 122 is only 10-20 um and is soft polymer material, the suspension is easy to deform in its tongue region 128 during the suspension manufacture process, the ultrasonic cleaning process or the HGA manufacture process, as well as a vibration or shock event. This will cause a dimple separation and seriously affect the HGA performance. FIG. 2a and FIG. 2b show a suspension tongue region deformation and a dimple separation respectively. Since the flexure 122 is easy to deform which easy causes the HGA dimple separation, and because the slider 103 is mounted on the top surface of the flexure 122, the static attitude of the slider 103 is difficult to control, which will seriously affect the HGA dynamic performance.
In addition, the shock performance of the full structure indicated above is very poor. When a vibration or shock event happens, the suspension or the PZT elements may be caused to damage, such as crack or broken.
Furthermore, because of the structure indicated above, the static angle in both pitch and roll direction are very poor. This will cause the HGA performance unstable and seriously affect the HGA dynamic performance, especially when a vibration or shock event happens during the manufacture process or handle process.
Hence, it is desired to provide an improved suspension, a HGA with a micro-actuator and its manufacturing method, and a disk drive unit with such HGA to solve the above-mentioned problems and achieve a good performance.